Electronics > RF, Microwave, Ham Radio

how to control LTDZ MAX2870 23.5-6000Mhz signal source?

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biastee:
I bought a "LTDZ MAX2870 23.5-6000Mhz signal source" (attached image), which is available from all the major online platforms.  However it didn't come with any instruction.

There are 5 tact switches on the PCB, covering the following functions: <, >, ^, v, and OK. I can change the frequency thru these switches, but for the life of me, I can't figure out how to manually change the amplitude. In the attached photo, the amplitude is displayed on the bottom row of the display.

There is a frequency sweep function, but I can't figure how to start the sweep.

According to the advertisement, the item can be PC controlled, but no software is provided. When I tried to connect with the MAX287X PLL EV Kit Software, it couldn't detect the signal source (error message in attached image below).

Thanks.

[attach=1]

ledtester:
A couple of things...

Banggood sells the same device:

https://www.banggood.com/Geekcreit-LTDZ-MAX2870-STM32-23_5-6000Mhz-Signal-Source-Module-USB-5V-Power-Frequency-and-Sweep-Modes-p-1696744.html

and if you follow the link >>>Instruction: Click here to open<<< it brings you to this low-level protocol documentation:

http://myosuploads3.banggood.com/products/20200618/20200618202558MAX2870STM32RF.pdf

Also, Tony Albus has both the ADF4351 and MAX2870 versions, and in this video he shows the same control program operating both the ADF4351 and MAX2871 (at time 21:29):

#129 MAX2870 LCD Signal Generator vs ADF4351 LCD Review Teardown -- Tony Albus
https://youtu.be/DFtC7icVr-E&t=21m29s

and he thanks the ebay store "pincei_de" for the control software:

[attach=1]

Tony is also on this forum (username "tonyalbus"), so you might contact him.

The MAX2870 and ADF4350 are very similar -- here's a Maxim app note comparing the register layout in both devices:

App Note 5498 - Comparing the Registers and Loop Filter of the MAX2870 and ADF4350 Synthesizers
https://pdfserv.maximintegrated.com/en/an/AN5498.pdf

ledtester:
Here is some more info which may be of interest...

This is a very comprehensive video on a particular ADF4351 module and one thing it does is it explains how the Analog Devices eval board and software interact with each other:

[005] 4.4GHz RF Synthesizer Board - ADF4351 - Theory, Setup, Reverse Engineering, Experiments -- OpenTechLab
https://youtu.be/xJ0Mfuj0KUQ

By reverse engineering the eval board and software the author was able to write a python library to control any ADF4351 from a PC. You still need a way for the PC to send SPI commands to the ADF4351 and the python library has code which interfaces with a Bus Pirate USB device for this purpose.

The python library may be found here:

https://github.com/jhol/pyadf435x

The main thing this library has is the logic which figures out what the ADF4351 control register values should be to generate a particular output frequency.

richard.cs:

--- Quote from: biastee on December 07, 2021, 05:15:00 am ---When I tried to connect with the MAX287X PLL EV Kit Software, it couldn't detect the signal source

--- End quote ---
I have used the official eval kit at work recently. It has a PIC on the board that pretends to be a USB-HID, and forwards raw register contents on to the synth. The protocol for this USB HID is entirely undocumented but fairly straightforward to reverse-engineer.

I suspect these cheap modules have a totally different interface.

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